Fixation bail

ABSTRACT

A bail ( 20 ) for an expansion shell assembly which is formed from a continuous elongate metallic member shaped to have a yoke ( 24 ), at least two U-shaped legs ( 26,28,30 ) which extend from the yoke, and a biasing element ( 76 ) which projects from the yoke.

BACKGROUND OF THE INVENTION

This invention relates generally to a rock or anchor bolt and, moreparticularly, is concerned with a bolt of this type which makes use of amechanically activated expansion shell assembly.

An expansion shell assembly typically includes a wedge member and anumber of leaves which are held together, at spaced locations around thewedge member, by means of a bail. Each leaf is directly attached to aleg of the bail by means of spot welding or the like.

FIG. 1 of the accompanying drawings illustrates a sheet metal blank 10from which bails of the aforementioned kind are made. An opening 12 inthe blank outlines material which is removed to form a bail. Each bailhas a central, circular yoke 14 and (in this case) three legs 16 whichare integrally formed with the yoke and which are spaced apart at 120degrees from each other. The plate 10 typically is about 1 millimetrethick.

The bails are precisely positioned on the strip 10 to minimize theproduction of waste material when the bails are stamped or otherwiseformed from the strip 10. Nonetheless a substantial amount of wastematerial is produced—this is evident from an inspection of FIG. 1 inwhich a hatched area 18 represents material within the strip which iswasted or which otherwise must be recovered for recycling or similarpurposes.

It is an object of the invention to provide a bail in which thegeneration of waste material is substantially eliminated. This helps tocontain costs.

SUMMARY OF THE INVENTION

The invention provides a bail for an expansion shell assembly whichincludes a body which has a yoke and a number of legs extending from theyoke and which is formed from an elongate member.

The elongate member is preferably a continuous elongate length of metale.g. wire or a thin rod.

The yoke may be formed at least partly by one or more sections of theelongate member which bound, at least partly, a central region of thebody.

The central region may be substantially circular in outline.

A portion of the elongate member may extend across the yoke.

The portion of the elongate member may be secured to the yoke e.g. byspot welding the portion to the yoke at a location at which the portionoverlies, and is in contact with, the yoke, or by crimping the portion,e.g. at an extremity, to the yoke.

Each leg may be of any suitable shape and preferably is in the form ofan elongate U. Extremities of the U are conveniently shaped tofacilitate attachment of each leg to a respective leaf in an expansionshell assembly.

The bail may include a biasing element. Preferably the biasing elementis formed from part of the elongate member. The biasing element may beof any suitable shape or form.

The biasing element may extend from the yoke. Preferably the biasingelement is in the form of a coil spring which projects from one side ofthe yoke.

The invention also extends to an expansion shell assembly which includesa wedge member, a plurality of leaves which are positioned at spacedlocations around the wedge member, and a bail of the aforementionedkind, and wherein each leg of the bail is attached to a respective leaf.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further described by way of examples with reference tothe accompanying drawings in which:

FIG. 1, which has already been referred to hereinbefore, relates toprior art bails;

FIG. 2 is a plan view of a bail according to a first form of theinvention;

FIG. 3 is a side-view of an expansion shell assembly which makes use ofa bail of the kind shown in FIG. 2; and

FIG. 4 is a perspective view of a bail according to a second form of theinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 2 of the accompanying drawings illustrates a bail 20 according to afirst form of the invention which is manufactured on a CNC wire bendingmachine using an elongate metallic member, e.g. a length of wire 21 of asuitable diameter.

The wire bending machine is programmed using techniques which are knownin the art to bend the wire 21 into a desired shape. During productionthe wire is shaped at great speed and with substantial economy inmaterial. No scrap wire is generated and material handling processes andthe costs associated therewith are greatly reduced.

In this example the bail 20 has a body 22 with a central yoke 24 andthree legs 26, 28 and 30 which extend from the yoke. The yoke is formedat least partly by a number of sections 32, each of arcuate shape, whichbound a central region 34 of the body which is substantially circular inoutline.

Adjacent legs are spaced apart from each other, in an angular sense, byabout 120°. Each leg is in the form of a elongate U and includesopposed, spaced parallel limbs 36 and 38 respectively and a bridging,curved portion 40 at an outer extremity of the limbs.

An end section 42 of the wire 21 extends centrally into the circularregion bounded by the yoke. At a location 44 where a part of the section42 overlies, and is in contact with, a part of the yoke, the section 42is secured to the yoke, e.g. by using an automated spot weldingtechnique. The two wire parts could alternatively be fixed together bymechanically deforming e.g. crimping one or both parts, or by wrappingor twisting the end section 42 around the yoke.

It is apparent from a comparison of FIG. 1 and FIG. 2 that the bail 20conforms in outline substantially to the bail opening 12 shown in FIG.1.

The yoke 14, of a bail made using the technique shown in FIG. 1,consists of a solid piece of the sheet material. In the bail 20 the yoke24 is not continuous and the section 42 is formed to enable the wirebail to act, effectively, in the same way as the sheet metal bail.

FIG. 3 is a side view of an expansion shell assembly 50 which includes acentrally positioned wedge member 52, only a small portion of which isvisible, three leaves 54 which are positioned at locations which arespaced apart by 120° from each other around the wedge member, and a bail20 of the kind shown in FIG. 2. The yoke 24 overlies a central portionof the wedge member and the legs 26, 28 and 30 are folded, from theplanar arrangement, shown in FIG. 2, through 90° so that each leg partlyoverlies a respective leaf 54. An extremity of each leg is tack-weldedto a respective leaf 54. Alternatively, as shown in FIG. 3, a smallrivet or similar upset member 56 is deformed to secure the leg to theleaf. The latter process can be facilitated, if required, by bending thewire at the curved portion 40 of each leg, into a closed loop e.g. acircle 60 as is shown for the leg 30 in FIG. 2.

An advantage of using a CNC wire bending machine is that the wire whichforms the bail can be shaped, within reason, in any appropriate way tofacilitate attachment of the bail to the leaves of the expansion shellassembly. Although the bail is preferably formed from a continuouslength of wire it could be formed from two or more wire lengths but, inthis event, there would normally be attendant costs and technicalimplications.

The section 42 overlies the mouth of a passage which extends centrallythrough the wedge member and functions, in use of the expansionassembly, in a manner which is similar to the way in which the solidyoke 14 shown in FIG. 1 functions.

FIG. 4 shows, in perspective, a bail 64 according to a second form ofthe invention which is also made on a CNC wire bending machine using anelongate length of wire 66. The bail 64 has a central yoke 68 ofgenerally circular outline and legs 70, 72 and 74 which are generallythe same as the legs shown in FIG. 2 and which are positioned atlocations spaced apart by 120° around the yoke 68. The bail includes anintegrally formed biasing element 76 in the form of a helical coilspring which is centred on the yoke 68 and which, in use, is oriented toface onto the centrally positioned passage, referred to in connectionwith FIG. 3, in the wedge member 52. At a location 44A, on the yoke,overlapping parts of the wire 66 which contact each other are spotwelded together. This stiffens the bail and helps the bail to retain itsshape during installation of the expansion shell assembly. For reasonswhich are known in the art and which are not further described hereinthe inclusion of the biasing element, integrally provided with theremainder of the bail, substantially facilitates use of the expansionshell assembly when a rock bolt is installed.

1-13. (canceled)
 14. A bail for an expansion shell assembly including: abody having a yoke and a number of legs extending from the yoke andformed from an elongate member, the bail comprising: a biasing elementformed from part of the elongate member.
 15. The bail according to claim14 wherein the elongate member comprises a continuous elongate length ofmetal.
 16. The bail according to claim 14 wherein the yoke is formed atleast partly by one or more sections of the elongate member which bound,at least partly, a central region of the body.
 17. The bail according toclaim 16 wherein a portion of the elongate member extends across theyoke.
 18. The bail according to claim 14 wherein each leg is in the formof an elongate U and includes opposed, spaced, parallel limbs and abridging portion at an outer extremity of the limbs.
 19. The bailaccording to claim 18 wherein the bridging portion of each leg is formedinto a closed loop.
 20. The bail according to claim 14, wherein at theyoke, a first part of the elongate member is secured to a second part ofthe elongate member by welding, or by mechanical deformation of at leastone part.
 21. The bail according to claim 14 wherein the biasing elementcomprises a coil spring on one side of the yoke.
 22. A bail for anexpansion shell assembly formed from a continuous elongate metallicmember shaped to have a yoke, and at least two U-shaped legs whichextend from the yoke, the bail comprising a biasing element projectingfrom the yoke, and configured as a helical coil.
 23. A bail for anexpansion shell assembly formed from a continuous elongate metallicmember shaped to have a yoke, and at least two U-shaped legs extendingfrom the yoke, the bail comprising: a biasing element projecting fromthe yoke, and wherein at the yoke, a first part of the elongate memberoverlies, and is in contact with, a second part of the elongate member,and the first part is secured to the second part by welding or bymechanically deforming at least one of the parts.
 24. An expansion shellassembly having a wedge member, and a plurality of leaves positioned atspaced locations around the wedge member, the expansion shell comprisingthe bail according to claim 14, and wherein each leg of the bail isattached to a respective leaf.